The present invention relates to data synchronous transfer systems, and more particularly, to data processing apparatus comprising nodes provided to data processing apparatus or peripheral apparatus and disposed at a plural number of points which are mutually separated by a certain distance, and optical transfer cables connecting those control apparatus, and provided with a fiber distributed data exchange interface (hereinafter termed an FDDI) that can be used for optical local area networks to transmit/receive at either high speed or low speed, various types of data between said processing apparatus and/or control apparatus, and peripheral apparatus, and relates to data synchronous transfer methods that have circuit exchange functions such as the cyclic performing of data, exchange between control apparatus at a plural number of mutually remote locations, the simultaneous sampling of process data such as instantaneous values such as voltage, current and the like, at a plural number of mutually remote locations, the enabling of data transfer so that a plural number of computers and control apparatus are connected with all processing apparatus performing data processing in temporal synchronization, and that can transfer data such as the voice data necessary for cyclic transfer, and the like.
In recent years, local area networks (hereinafter, termed LAN networks) have been used at an increasing rate in many different fields. Amongst these fields, one that is attracting much attention in the field of next generation, high-speed and wide-area LAN are fiber distributed data exchange interfaces for which standardization has been defined by the American National Standards Institute (hereinafter, termed ANSI-FDDI). These ANSI-FDDIs use optical fiber as the transfer path and are 100 Mbps ring-shaped LAN that use the token passing method as the transfer control method. Although the ANSI has practically completed the standardization of the FDDI ratings, FDDI are being studied in the fields of the computers and communications industry since largescale integrated circuits (hereinafter, termed LSI) and protocol processing software in conformity with the FDDI ratings has come to be available from semiconductor manufacturers.
For example, one proposal has been for the use of FDDI to configure a packet exchange network so that data can be both sent and received at high speeds between multiple mainframe computers, between mass storage systems connected to mainframe computers, or connecting between mainframe computers and other peripheral equipment. Furthermore, these FDDI are thought to be capable of being used as backbone networks connecting between LAN systems for low-speed data transfer and receive such as in the case of the Ethernet and MAP (manufacturing automation protocol, hereinafter abbreviated MAP) systems and the like.
MAP is a communications protocol for the automization of factories and is the practical standard for LAN for factory automation purposes (known as FALAN). LAN using FDDI having a plural number of nodes mutually connected in a ring shape generally have various functions such as transfer path control functions that can stop transfer requests from each node, in accordance with the transfer region that can be used by the network and acquire transfer path usage rights, transfer and receive function for the data from each node, transfer system obstruction detection functions, obstruction portion separation functions, and transfer system reconfiguration functions, etc.
As has been described above, in token-passing LAN used for LAN having FDDI, transfer rights known as tokens are successively received between each of the nodes in the system to prevent a plural number of nodes from sending at the same time. These systems are configured so that data can be sent within a predetermined set time, by those nodes that have received tokens. Accordingly, it is possible to have definitive transfer path access and so this token passing method is used in MAP systems that require real time control.
It is necessary to use the wide-area characteristic of FDDI for the transfer of data which is a combination of voice data, image data and other types of data. For example, in the transfer of voice data, cyclic transfer for each multiple of time of 1/8 KHz 125 .mu.sec is necessary in order to accommodate a voice band of 8 KHz and it is possible to transfer data cyclically using current FDDI that are based on the packet exchange method. However, in LAN systems that use current FDDI, because of cumulative errors, there is the problem of it not being possible to transfer the data that is necessary for the cyclic transfer of data such as voice data.
However, when a ring-shaped high-speed LAN using a FDDI is used to transfer data, it is desirable to develop a data transfer system that has the data packet exchange functions conventionally provided, and for it to additionally have circuit exchange functions such as the cyclic performing of data exchange between control apparatus at a plural number of mutually remote locations, the simultaneous sampling of process data such as instantaneous values such as voltage, current and the like at a plural number of mutually remote locations, the enabling of data transfer for so that a plural number of computers and control apparatus are connected with all processing apparatus performing data processing in temporal synchronization, and that can transfer data such as the voice data necessary for cyclic transfer, and the like.